Disorder, Topology and Frustration in Quantum Materials

University Of Minnesota-Twin Cities, Minneapolis MN

Investigators

Abstract

NONTECHNICAL SUMMARY This award supports theoretical research with an aim to understand the effects of disorder in a novel phase of matter called the quantum spin liquid. In this unique phase, electron spins in a material do not establish ordered patterns, even at zero temperature, as they normally do in conventional magnets, but remain liquid-like due to the peculiarities of quantum mechanics. This phase has been a central theme in condensed matter physics for decades, both from a fundamental perspective and in terms of its potential applications in novel technologies, such as their promise for building robust quantum computers. It is known that the properties of the spin liquid phase in real materials can be modified or destroyed in the presence of disorder, such as atomic imperfections due to missing atoms or impurities. In this project, the PI and her team will investigate how different types of disorder in real materials can suppress or enhance the discernibility of quantum spin liquid phase and the unique quantum mechanical properties associated with this phase. This theoretical research will be conducted in close collaboration with experimental studies. This award also supports the PI's educational and outreach activities that are linked to the research projects. Graduate and undergraduate students will be trained in condensed matter physics with a particular eye toward broadening participation of underrepresented groups in the research projects. The PI will also organize summer schools on modern condensed matter physics and collaborate with the Weisman Art Museum at the University of Minnesota to develop a new program for undergraduate students that combines artistic and scientific disciplines. TECHNICAL SUMMARY This award supports theoretical research with an aim to understand frustration and disorder effects in quantum magnets with strong spin-orbit coupling, non-trivial topology and correlations. This broad field has recently experienced significant advances in both theory and experiment. In particular, the quantum spin liquid phase has been one of the central themes in condensed matter physics, owing to their remarkable emergent properties, including long-range entanglement, topological degeneracy and fractionalized excitations. A growing number of candidate magnetic materials are believed to be adequately described by quantum spin liquid models. Some level of disorder is inevitable in real quantum spin liquid candidate materials, which makes it necessary to understand the competition between quantum fluctuations and randomness in order to unveil the true nature of their low-energy phase. One of the main goals of this project is to expand the current understanding of the effects of disorder in quantum magnets. The PI will study how quantum spin liquids respond to various forms of disorder, such as dislocations, vacancies, impurities, and bond randomness. A second goal of this project is to understand novel quantum phases arising from a collective behavior of correlated electrons in the presence of strong spin-orbit coupling and non-trivial topology. The PI will study both candidate materials and theoretical models proximate to the Kitaev honeycomb model and, more generally, on systems with strongly anisotropic bond-dependent interactions. This award also supports the PI's educational and outreach activities that are linked to the research projects. Graduate and undergraduate students will be trained in condensed matter physics with a particular eye toward broadening participation of underrepresented groups in the research projects. The PI will also organize summer schools on modern condensed matter physics and collaborate with the Weisman Art Museum at the University of Minnesota to develop a new program for undergraduate students that combines artistic and scientific disciplines. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.